Introduction to Dermatology Flashcards
Functions of the skin (7) and structure/cells involved
- Decoration=skin, hair, nails, lips
- Barrier
- physical=epidermis: keratinocytes
- light=epidermis: melanocytes
- immunologic=epidermis: langerhans cells
- Vitamin D synthesis=epidermis: keratinocytes
- Water homeostasis=epidermis: keratinocytes & Adnexa: eccrine glands
- Thermoregulation=adnexa: eccrine glands & dermis: blood vessels
- Insulation/Calorie Reservoir=subcutaneous fat
- Touch/sensation=dermis: nerves
Structure/Cells involved in: 1. grasp 2. lubrication of skin 3. pheromones/body odor
- grasp=adnexa: nails
- lubrication=adnexa: sebaceous glands
- pheromones/body odor=adnexa: apocrine glands
Structure/cells involved in strength and elasticity of skin
-dermis: fibroblast –> produces collagen and elastin
Characteristics of Fitzpatrick Skin Type I: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: red/blond
- Eyes: blue/green
- Skin: white
- Freckles: +++
- Sunburn: always
- Tan: 0
Characteristics of Fitzpatrick Skin Type II: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: blond/brown
- Eyes: light to Medium
- Skin: fair
- Freckles: ++
- Sunburn: easily
- Tan: minimally
Characteristics of Fitzpatrick Skin Type III: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: brown
- Eyes: medium to dark
- Skin: light
- Freckles: +
- Sunburn: initially
- Tan: gradually
Characteristics of Fitzpatrick Skin Type IV: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: medium to dark
- Eyes: dark
- Skin: moderate brown
- Freckles: 0
- Sunburn: minimally
- Tan: tans well
Characteristics of Fitzpatrick Skin Type V: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: dark
- Eyes: dark
- Skin: dark brown
- Freckles: 0
- Sunburn: rarely
- Tan: dark tan
Characteristics of Fitzpatrick Skin Type VI: Hair, Eyes, Skin, Freckles, Sunburn, Tan
- Hair: dark
- Eyes: dark
- Skin: black
- Freckles: 0
- Sunburn: never
- Tan: always tan
Major components of the skin (4)
- Epidermis=stratified squamous epithelial layer
- Dermis= underlying connective tissue layer= papillary layer (loose connective tissue) + deeper reticular layer (dense connective tissue)
- Adnexal structures: Apocrine glands, Eccrine glands, hair, nails, Sebaceous glands
- Subcutaneous fat=adipocytes
Characteristics of thick skin
- hairless
- found @ palms and soles of feet
Layers of epidermis (superficial –> deep)
- stratum corneum
- stratum lucidum (thick skin only)
- stratum granulosum
- stratum spinosum
- basal layer
Characteristics of keratinocytes
- form barrier layer
- synthesize keratin –> intracellular fibrous protein
- defined cycle of proliferation, differentiation, and apoptosis
Characteristics of melanocytes
- pigment-producing cells (melanin <– tyrosine)
- located @ basal layer of epidermis, hair follicles
- melanin packaged in granules (melanosomes) and transfered to ~30 neighboring keratinocytes via dendritic processes
- melanin protects DNA from UV damage
Characteristics of Langerhans cells
- small amounts present in all epidermal layers
- dendritic cells in epidermis
- cell-mediated immune reaction participation through processing and presentation of antigens
Main factors determining skin color variation
- type of melanin produced
-eumelanin=black to brown pigment
-pheomelanin=yellow to red-brown pigment - distribution of melanosomes
-light skin=melanosomes in clusters above
nucleus
-dark skin=melanosomes distributed individually
throughout the cytoplasm
General life cycle of keratinocytes
- epidermis continually renewed by mitosis of keratinocytes in basal layer and shedding @ surface
- entire cycle=28 days
Basal cell layer (stratum basalis) characteristics
- deepest layer of epidermis
- single layer of columnar or cuboidal cells (keratinocytes)
- basal keratinocytes=stem cells of epidermis
Important keratinocyte cell attachments (3)
- hemidesmosomes: attach basal cells to basal lamina
- desmosomes: attach keratinocytes to each other
- tonofilaments: keratin filaments that insert into dense plaques of desmosomes on cytoplasmic side of plasma membrane
Stratum spinosum characteristics
- layer just superficial to basal layer
- “prickly” apperance b/c desmosome attachments
- intercellular adhesion dependent on tonofilament-desmosome interactions
- synthesis of involucrin and membrane-coating granules begins here
Stratum granulosum characteristics
- cells contain granules
- Keratohyalin granules contain Profilaggrin (filaggrin precursor).
- Filaggrin cross-links keratin tonofilaments and is important in the barrier function of the skin.
Stratum lucidum characteristics
- thin, light staining band seen only in thick skin
- cells have no nuclei or organelles
Stratum corneum characteristics
- outermost layer of epidermis
- keratinocytes have lost nuclei and organeles
- entire cell filled w/keratin
- desmosomes still connect tightly packed adjacent cells
Papillary layer characteristics
- superficial layer of dermis
- attaches to epidermis
- contains capillary network that is blood supply for epidermis
- pathway for defense cells
- contains Messner’s corpuscles which sense touch
Reticular layer characteristics
- deeper layer of dermis
- extensive collagen/elastin fibers –> strength and flexibility
- houses epidermal derivatives (glands, hairs) and plays role in their development and fxn
- pathway for bvs that facilitate thermoregulation
- site of nerve tracts and major sensory receptors
- pacinian corpuscles sense vibration, pressure, and touch
Meissner’s corpuscles characteristics
- detect delicate touch
- found in the dermal papillae of thick skin
- consist of Schwann cells and sensory nerve terminals wrapped by fibroblasts and collagen
Pacinian copuscles
- receptors that detect changes in deep pressure (vibrations)
- found in the dermis of both thin and thick skin
- large structures resembling an onion
- the concentric layers are composed of flattened connective tissue-like cells interspersed with intercellular fluid and collagen
- a single sensory nerve fibers terminates within this structure
Apocrine sweat gland characteristics
- specialized sweat glands located in the axillary, pubic and perianal regions
- produce a milky, viscid, carbohydrate-rich secretion that is initially odorless
- bacterial action on secretions leads to a characteristic axillary body odor
- begin to function in puberty
- have ducts which empty into hair follicles just above sebaceous glands
Eccrine sweat gland characteristics
- Traditional sweat glands distributed over most of the body
- Not found in the lips, under the nails or on the glans penis, glans clitoris, or labia minora
- Watery, enzyme-rich secretion, initially isotonic, becomes hypotonic as Na+ is reabsorbed by the ducts
- Important for thermoregulation
Hair characteristics
- Develop in utero with downgrowth of the epidermis forming a pilosebaceous unit
- The hair itself consists of a central medulla of soft keratin, and a cortex and cuticle of hard keratin.
- Hair growth is intermittent
- Pigment comes from melanocytes at the base of the hair
- With contraction of the arrector pili muscle (smooth muscle), hairs stand on end (“goose bumps”)
Sebaceous glands characteristics
- Oil glands which secrete sebum=a complex mixture of lipids
- develop along with hair follicles and empty their secretion into the upper one-third of hair follicles
- development accelerated at puberty
